Technical Field
The disclosure relates to a method and a device for data transmission, and particularly relates to a non-orthogonal multiple access data transmission method and a transmission device.
Description of Related Art
Since non-orthogonal multiple access (NOMA) techniques are capable of providing higher transmission efficiency than conventional orthogonal multiple access techniques with the same bandwidth resources, the NOMA has been viewed as one of the candidates for the multiple access technology of fifth generation wireless systems.
In the NOMA system, multi-user multiple access is performed in the power domain of the transmitting terminal, and then multi-user signals are separated by employing successive interference cancellation (SIC) techniques at the receiving terminal. Specifically, in order to correctly modulate multiple user data sent by the base station at each user equipment terminal, the NOMA system, in the case where the total transmit power is fixed, allocates more transmit power to the user equipment with inferior channel conditions while allocating less transmit power to the user equipment with better channel conditions. In this way, the user equipment terminal may perform decoding and obtain the user data belonging to itself by implementing the SIC techniques. However, there are still some problems waiting to be solved regarding such NOMA scheme achieved by power adjustment. For example, since the transmit power is determined by the base station according to the location of the user equipment, when the locations of a plurality of user equipments are close to one another, each of the allocated transmit power likewise becomes similar Thus it is easy to result in reduced efficiency and accuracy of the user equipment in implementing the SIC techniques.
Consequently, for a person skilled in the art, how to solve the problem of reduced bandwidth efficiency caused by signal interference among the closely located user equipments in the NOMA system is indeed an issue of concern.